1. Field of the Invention
The present invention relates to a coating device for forming uncoated regions elongated in the transverse direction of a base material among contiguous coated films by intermittently discharging a coating solution from a slender discharge port toward the transferring base material.
2. Description of Related Art
There has been a conventional publicly-unknown coating device for carrying out coating intermittently as is illustrated in FIG. 16. The coating device 1 is provided with a backing roll 2 on the outer peripheral face of which a base material transfer path R is formed and which is driven to rotate in the direction of an arrow E and a die main body 3 intermittently discharging a coating solution toward the base material transfer path R. According to the die main body 3, a slender discharge port 4 facing the base material transfer path R is extended along the transverse direction of the base material transfer path R at a trailing end of a path 5 for a coating solution which is formed at the inner portion of the die main body 3. The die main body 3 is provided with an opening and closing valve 6 for opening and closing the path 5 for a coating solution. A primary manifold 5a is formed in the path 5 for a coating solution upstream from the opening and closing valve 6 and a secondary manifold 5b is formed therein downstream from the opening and closing valve 6. When a coating solution is pressurized and supplied from a coating solution supply pump, not illustrated, to the primary manifold 5a, the opening and closing valve 6 distributes the coating solution uniformly to all the open regions of the path 5 for the coating solution and discharges the coating solution uniformly from all the regions in the longitudinal direction of the discharge port 4 toward the base material transfer path R
According to the coating device 1, if the opening and closing valve 6 of the die main body 3 is opened for a predetermined period of time during which the base material W comprising paper, plastic film, metal foil or the like that is backed by the backing roll 2, is being transferred coating films A are formed by coating the coating solution from the discharge port 4 onto the base material W and if the opening and closing valve 6 is closed for a predetermined period of time, uncoated regions B are formed on the base material W by stopping the discharge of the coating solution from the discharge port 4. By repeating the opening and closing operation of the opening and closing valve 6 the uncoated regions B in a strip-like shape elongated in the transverse direction of the base material W are formed on the surface of the base material W by a desired strip width dimension C at given intervals.
Meanwhile, even if the path 5 for the coating solution is closed by the opening and closing valve 6, the coating device 1 cannot immediately stop the coating solution from discharging from the discharge port 4. The reason is that the coating solution under a pressurized state passes through the path 5 for the coating solution before closing the opening and closing valve 6 and therefore, even if the opening and closing valve 6 is closed, the coating solution starts to leak from the discharge port although the amount thereof is very small, until the coating solution remaining in the path 5 for the coating solution downstream from the opening and closing valve 6, is decompressed.
However, the leakage of the small amount of the coating solution from the discharge port 4 after closing the opening and closing valve 6, poses a problem where a portion having a thin film thickness is formed at a trailing end Aa of the coated film A formed on the base material W and the film thickness of the coated film A cannot be made uniform from the leading end to the trailing end thereof.